Thanks for the fantasy

More than an hour before Terry Pratchett is due to start signing books, a small queue of his readers has already formed under the bright retail lights of WH Smith in Croydon. There is a lean man with a ponytail, a young mother with a silent baby, a middle-aged man in tweeds and a wheelchair. At the front is a teenage girl, dressed all in black and sitting cross- legged on the floor, head bent forward, reading. She has brought a whole carrier bag of Pratchett with her.

"It's nice to meet the fans," says Pratchett rather automatically, waiting too, in a small grey cell of an upstairs staff room. "It keeps you in touch." Outside the window, the first day of summer warms the half-term streets; but shut in here, Britain's most fanatically followed novelist bounces contentedly back and forth in an office chair, a hundred pre-ordered copies of his new fiction, Feet Of Clay, stacked up behind him. Ahead of schedule, he has signed them all.

Pratchett is a small bear of a man, white-bearded and 48. In his olive shirt and baggy chinos, he could almost pass for Umberto Eco, but he is far more prolific. Every year since 1987 he has published at least two fine-detailed fantasy novels. Feet Of Clay is the nineteenth in a labyrinthine series called Discworld, and there have been separate trilogies for teenagers, as well as a bewildering number of one-off volumes. He sells around a million novels a year. One out of every 50 books bought from WH Smith is his. Shoplifters favour him too.

Pratchett affects to find all this enthusiasm slightly puzzling: "There suddenly seems to be an explosion of Discworld consciousness in Prague," he says in his rough-vowelled Buckinghamshire voice, explaining that the craze started with the wife of the Czech foreign minister. But this is charm. Discworld's cutely imagined city of police gargoyles and talking dogs has long been popular enough for a computer game spin-off, Discworld maps and Discworld figurines. At the end of this month the first Discworld convention is to be held in a Manchester hotel. Even A S Byatt says she is a fan.

Pratchett's cleverness has been to take the generally low-status genre of fantasy, or sword and sorcery fiction - known in the trade as "stabbing and tricks" - and make it laugh at itself. In his 1987 book Mort, the figure of Death, ghosting along a cobbled street, slips over on a patch of ice. Feet Of Clay opens with the discovery of a corpse, battered to death with a rock-hard baguette from a Dwarf Bread Museum. This mix of the portentous and the banal has worked as well for Discworld as it did for Monty Python and The Hitchhiker's Guide To The Galaxy. Its cheekiness is very English. At the same time, Pratchett slyly brings elements of everyday life into his fantasy world and lets the two rub together. In Discworld, television sets work because imprisoned gnomes are painting frantically behind the screen.

Yet for all his genre-mockery, Pratchett has also constructed an imaginary world every bit as detailed as those of Tolkein and his imitators. Discworld itself is described as a kind of cosmic plate, carried on the backs of four giant elephants which themselves stand on the shell of a vast "star turtle" as it plunges through space. Such delights, for certain minds, can be found too in the city-state Pratchett places at Discworld's centre, called Ankh-Morpork, a Gothic maze through which he guides readers, street by street and book by book, with the roaming inventiveness of a good computer game. And there is one benign difference: hardly anyone gets killed.

PRATCHETT learnt early to put tricks before stabbing. As a teenager in Beaconsfield in the early Sixties, he spent days in the public library, soaking up Paradise Lost. Home was a cottage with no electricity and his parents out working all day - his mother as a secretary, his father as a mechanic. Tearing round fields, pushing friends into stinging nettles had lost its appeal.

The young Pratchett persuaded his parents to let him go to a science fiction convention. When he got there -"standing next to me in the queue was Arthur C Clarke" - Pratchett thought he would be a writer. His first published story was called The Hades Business and was denounced by his headmaster at Wycombe Technical School for debasing its magazine.

At 17, in 1965, Pratchett left school to join the Bucks Free Press as a reporter. Local journalism demystified writing: "You get less excited about seeing your name in print. You don't get scared of a sheet of paper... You are aware that you have readers." He had already finished his first novel, an ingenious children's saga about miniature tribes living on a carpet called The Carpet People, but it took three years to find a publisher. Colin Smythe Publishing Ltd only sold 3,000 copies (they go for pounds 300 each now; the 1992 reprint made the adult bestseller lists), and Pratchett lived a part-time writer's life during the Seventies, squeezing in a few hundred words a night. In 1980 he put his cheeriness to a new daytime purpose: soothing away anxieties about nuclear power stations as a press officer for the Central Electricity Generating Board. He "never knowingly lied".

PRATCHETT was rescued from this by a turtle-borne disc. In 1983 he finished a fourth and different novel, The Colour Of Magic, set, for the first time, on Discworld. The book was read out on Woman's Hour and gradually, as he produced sequels, Discworld went from conceit to phenomenon. By 1987, "the success was going faster than my ability to comprehend it." So Pratchett chose not to; instead, he hid in his cottage in the Mendips ("life was an eternal search for free wood"), and wrote faster. The series acquired the following and gentle repetitions of a soap opera.

But Pratchett had other purposes too. Like Hobbes or Swift, he made his invented world a paddock for his hobby horses. Some of these were banal: Moving Pictures feebly mocked Hollywood, which became a rainless and narcissistic studio town called Holy Wood. Others have been less obvious: in Feet Of Clay gibbets swing at every corner of Ankh-Morpork, but only wooden dummies hang beneath them, creaking by clockwork, faith in real executions as a deterrent having long passed away. Meanwhile the city itself, a republic sliced up and sustained by all-powerful Guilds (even an Assassins' Guild, with rules about not killing bystanders), makes its own political inferences - even if Pratchett always denies them.

He prefers to talk about his writing: every day, starting soon after eight, with a toilet roll beside him for the snuffling winter months. "When you have that original spark or idea the mental radio starts to tune itself," he says, almost apologetically. Colin Smythe says: "He starts the next one on the afternoon he's finished the last one."

But there are limits to Pratchett's fecundity. "I'm not saying that if I stopped all this I could be a 'serious' writer," he admits. A planned detective series has so far proved abortive. And the Discworld books, for all their steadily rising credibility in the broadsheets, are still rarely taken seriously enough by literary editors to be reviewed by anyone other than Pratchett converts.

This is all irrelevant to his readers, of course. What matters to them, besides the books, is the bubbling cauldron of Pratchett-chat, the Internet disputes about motive and plot, the rumours of new and lost works. "The cod idea arose that I had posted a chapter on the Net to someone, and I had lost my original copy... This idea persisted for four years." Like followers of Star Trek, Discworld fans are not always content to let the writer decide the fates of their favourite characters. Pratchett and Colin Smythe, now his agent, receive plot suggestions, proposals for books and, most of all, complaints in the rare event that protagonists die.

Pratchett's wife Lyn sifts his mail. He is careful to husband Discworld, only allowing film companies the rights to a few books and protagonists at a time. "He already has more money than he knows how to spend," says Smythe. Recently Pratchett moved to a bigger house near Salisbury, with an outhouse for writing and a tennis court he doesn't use. His daughter Rhianna is old enough for public school, but he still listens to Meatloaf and fusses over his tortoises and favourite fly-catching plants. All he wants, he says, is to live to be old, "with all my faculties".

THAT may not be quite true. In Croydon, as in all the towns Pratchett tours, four days a week for several months a year, he nearly jumps from his chair when the signing moment comes. Grabbing his bag of pens, he walks fast down the store-room corridor to the shop with its patient Pratchett fans. There are 200 now - as many as for Frank Bruno, the store manager says. It is hot, and many are using their lunch hour, but they are not behaving like a queue: they are lost in their books, or chatting away about characters, or simply smiling.

The girl in black is still at the front. Pratchett installs himself behind a desk in the shop window and pours out all his pens and his rubber stamps. She steps forward with her carrier bag. He smiles, and says: "Haven't you ever heard the words 'sad person'?" Then he gives her five minutes.